A friction plate is formed in such a manner that a plurality of friction material segments fixed to an annular core plate, wherein a passage extends through from an inner diameter side to an outer diameter side and is defined between the plurality of friction material segments, and a forming portion for retaining air is provided on a bottom surface of the passage.
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16. A friction plate formed in such a manner that a plurality of friction material segments fixed to an annular core plate,
wherein a passage extends through from an inner diameter side to an outer diameter side and is defined between the plurality of friction material segments,
a forming portion for retaining air is provided on a bottom surface of the passage, and
the forming portion is provided with a surface of an adhesive agent applied on a surface of the core plate.
1. A friction plate formed in such a manner that a plurality of friction material segments fixed to an annular core plate, wherein a passage extends through from an inner diameter side to an outer diameter side and is defined between the plurality of friction material segments,
a forming portion for retaining air is provided on a bottom surface of the passage, and
the forming portion includes a projection, the projection has a radius of 0.1 to 1 mm, a height of 0.01 to 0.3 mm, and an area rate of 10 to 50% to the passage.
6. A friction plate comprising:
an annular core plate;
a plurality of friction material segments fixed to a first surface of the core plate, each friction material segment being spaced apart from an adjacent friction material segment in a circumferential direction of the annular core plate so as to define an oil passage between each adjacent pair of friction material segments, each oil passage extending from an inner diameter side to an outer diameter side; and
means for retaining air provided within one or more of the oil passages.
8. A friction plate comprising:
an annular core plate;
a plurality of friction material segments on a first surface of the core plate, each friction material segment being spaced apart from an adjacent friction material segment in a circumferential direction of the annular core plate so as to define an oil passage between facing sidewalls of each adjacent pair of friction material segments, each oil passage extending from an inner diameter side to an outer diameter side; and
one or more protrusions within at least one of the oil passages, each protrusion being formed on or from the first surface within said at least one of the oil passages and protruding in a direction perpendicular to the first surface,
wherein the one or more protrusions are constructed to retain air within the at least one of the oil passages.
2. The friction plate according to
3. The friction plate according to
4. The friction plate according to
5. A wet multiple-plate clutch comprising:
the friction plate according to
a separator plate disposed alternately with the friction plate in an axial direction.
7. The friction plate according to
wherein each oil passage is defined by radially extending sidewalls of the adjacent friction material segments, and
the means for retaining air is disposed between said sidewalls in the circumferential direction.
9. The friction plate according to
10. The friction plate according to
a plurality of radially extending projections spaced from each other in the circumferential direction so as to define minute grooves within the at least one of the oil passages.
11. The friction plate according to
12. The friction plate according to
13. The friction plate according to
a columnar projection protruding from the first surface and having a radius of 0.1 to 1 mm and a height of 0.01 to 0.3 mm.
14. The friction plate according to
15. The friction plate according to
17. The friction plate according to
18. The friction plate according to
19. The friction plate according to
20. The friction plate according to
21. A wet multiple-plate clutch comprising:
the friction plate according to
a separator plate disposed alternately with the friction plate in an axial direction.
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Field of the Invention
The present invention relates to a friction plate used for a clutch and a brake of automatic transmission of vehicle.
Description of the Related Art
Drag torque between a friction plate and a counterpart plate during idling in the wet multiple-plate clutch of automatic transmission is a part of driving resistance associated with fuel economy of vehicle and reduction thereof greatly contributes to fuel economy improvement and CO2 emission control of vehicle. Conventionally, an effect for reducing the drag torque between the friction plates and the counterpart plates has been obtained by an effect for discharging (separating and the like) oil through a groove on a friction surface of the friction plate or an oil path between friction materials. This is disclosed in Japanese Patent Application Laid-Open No. 2005-076759 and in Japanese Patent Application Laid-Open No. 2008-180314.
Further, regarding a problem of demand for reducing the drag torque on the friction plates, how viscous resistance of fluid lubrication can be reduced specifically in a low rotation region is a key to solve the problem. In this regard, as disclosed in Japanese Patent Application No. 2014-149484, a certain effect can be obtained at 1000 rpm or less of a relative number of rotations by providing a groove on a segment-shaped surface of the friction plate.
However, fuel economy regulation and emission regulation in vehicle become stricter year by year. And if specifically a current problem of reducing viscous resistance of fluid lubricant that is high in a low rotation region that is around 500 rpm of a relative number of rotations in which the drag torque on the friction plates is great, is solved, a friction plate of wet multiple-plate clutch for automatic transmission can contribute toward achieving the fuel economy regulation and the emission regulation in vehicle. However, currently (in each of the above-mentioned references), there has not yet been found a method for reducing the viscous resistance of fluid lubricant of the friction plates in the low rotation region.
Further, a separation effect between friction plates using oil discharge force and an effect for reducing the viscous resistance of fluid lubricant by improving discharge property of oil by a groove of the friction plate, both of which effects are intended to reduce the drag torque, can be obtained by increase of rotation so that those effects have not yet been obtained in the low rotation region.
Accordingly, an object of the present invention is to provide a friction plate of a wet multiple-plate clutch, which is provided with a forming portion to facilitate retention of a bubble between the friction material segments and to reduce drag torque in a low rotation region remarkably.
To attain the above object, a friction plate is formed in such a manner that a plurality of friction material segments fixed to an annular core plate, wherein a passage extends through from an inner diameter side to an outer diameter side and is defined between the plurality of friction material segments, and a forming portion for retaining air is provided on a bottom surface of the passage.
The forming portion (a minute groove, a projection and an uneven portion) for retaining a bubble provided between a friction material segments of the friction plate enables air (bubble in oil) present in a stopped state and a rotational state of the friction plates to be retained. As retention of bubble increases or occurs from an early stage of rotation, a state of gas-liquid multiphase flow can be made from the fluid lubricant at the early stage of rotation.
Thereby, the effect is exhibited in the low rotation region where a viscous resistance is great in oil filled fluid lubricant, and the drag torque specifically around 500 rpm of a relative number of rotations can be reduced remarkably.
A forming portion for retaining a bubble is formed between friction material segments not only to promote generation of air but to retain air easily. Air rises on a surface of a friction material so that shearing resistance of oil between the friction plate and the counterpart plate is decreased and the drag torque can be reduced in the low rotation region (specifically at around 500 rpm of relative number of rotations) remarkably.
The friction material segments opened outside are shaped in such a manner that a minute groove, a projection or an uneven portion is disposed in passages located in a forward direction with respect to a rotation direction of an opened groove to retain or generate air and the opened groove of the friction material becomes a negative pressure by rotation to retain air, so that the effect becomes more significant.
Although air is also discharged together with oil from a simple radial (radial) groove by centrifugal force, the passage is formed in a shape of a minute groove, a projection or an uneven portion so that the air going out is retained or reverted to the passage by generation of negative pressure in the rotation direction.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Each embodiment of the present invention will now be described in detail below in accordance with the accompanying drawings. It is noted that each of embodiments to be described below is an example of the present invention and it is needless to say that the present invention is not limited to each of the embodiments. In the drawings, the same components are denoted by the same reference numerals.
The term “air” used in the present specification generally refers to air present in lubricant, but also includes vapor or other air in the lubricant. Further, air is present as gas in lubricant but is generally present as a bubble.
The wet multiple-plate clutch 10 is constituted of a substantially cylindrical clutch drum 1, which is open at one end in an axial direction, a hub 4, which is disposed on the inner periphery of the clutch drum 1 and which coaxially and relatively rotates, annular separator plates 2, which are disposed on a spline 8 movably in the axial direction, the spline 8 being provided on the inner periphery of the clutch drum 1, and annular friction plates 3, each of which is disposed on a spline 5, which is provided on the outer periphery of the hub 4, alternately with the separator plates 2 in the axial direction, and which have friction surfaces to which friction material segments are fixed with an adhesive agent. Each of the separator plates 2 has a spline portion 2a, which engages with the spline 8, and each of the friction plates 3 has a spline portion 3a, which engages with the spline 5. There are provided a plurality of the friction plates 3 and a plurality of the separator plates 2.
The wet multiple-plate clutch 10 is provided with a piston 6, which pushes and fastens the separator plates 2 and the friction plates 3, and a backing plate 7 and a stopper ring 17 retaining the backing plate 7, which are provided on the inner periphery of the clutch drum 1 to retain the separator plates 2 and the friction plates 3 in a fixed state at one end in the axial direction.
As illustrated in
Friction material segments 12 and 13, which have predetermined friction coefficients, are fixed to both surfaces of each of the friction plates 3, which are retained by the hub 4 such that they are slidable in the axial direction. Alternatively, however, the friction material segments 12 and 13 may be provided on only one side of the friction plate 3. Further, the hub 4 has a lubricant supply port 15, which penetrates in the radial direction. Through the lubricant supply port 15, a lubricant is supplied from the inside diameter side to the outside diameter side of the wet multiple-plate clutch 10.
The wet multiple-plate clutch 10 having the foregoing construction engages (fastens) and disengages a clutch as described below.
In order to engage the wet multiple-plate clutch 10 in the disengaged state, an oil pressure is supplied to the hydraulic chamber 11 defined between the piston 6 and the clutch drum 1. As the oil pressure increases, the piston 6 moves to the right in the axial direction in
In order to disengage the wet multiple-plate clutch 10 again after the wet multiple-plate clutch 10 is set to the engaged state, the oil pressure to the hydraulic chamber 11 is released. Upon releasing the oil pressure, the urging force of the return spring (not illustrated) causes the piston 6 to move to the position where the piston 6 comes in contact with the closed end of the clutch drum 1. Thus, the wet multiple-plate clutch 10 is disengaged.
The friction material segment 12 is provided with an oil groove 12a, which is opened at an inner diameter side and is terminated in the friction material segment 12 at an outer diameter side, and oil grooves 12b, each of which is opened at the outer diameter side and is terminated in the friction material segment 12 at the inner diameter side.
The oil groove 12a is formed in the substantially center in a circumferential direction of the friction material segment 12. Further, two oil grooves 12b are formed at both sides of the oil groove 12a in the circumferential direction while sandwiching the oil groove 12a. The provision of the oil groove 12b opened at only the outer diameter side enables the oil dragged in the friction surface 25 from the oil passage 21 to be discharged to the outer diameter side smoothly, thereby making it possible to reduce drag torque during idling. A remarkable effect in reduction of drag torque can be obtained specifically in the low rotation region.
The oil passage 21 is defined between a friction material segment 12 and a friction material segment 12 to extend through from the inner diameter side to the outer diameter side of the friction plate 3. Accordingly, the friction material segments 12 and the oil passages 21 are alternately disposed in the circumferential direction.
As it will be appreciated from
The grooves 31 can be formed by machining (cutting or the like), molding processing (embossing or the like), laser machining or the like. Further, they can be formed directly on a surface, exposed to an oil passage 21, of the core plate 20 by similar processing methods without the adhesive agent 22.
The grooves 31 are formed by the above-mentioned processing method with unillustrated processing machine so as to be formed at intervals of 100 μm between the friction material segments 12 as the minute grooves. A length in a diameter direction of the grooves 31 may be set to a length similar to that of the friction material segment 12 in the diameter direction from the outer diameter side to the inner diameter side of the friction plate 3. However, the grooves 31 may be any length in a diameter direction and they can be shorter or longer than a length of the friction material segments 12 in the diameter direction.
The grooves 31 preferably have a width of 50 to 500 μm and a depth of 10 to 500 μm. If the width of the grooves 31 is smaller or equal to 50 μm, the effect cannot be obtained and if the width of the grooves 31 is greater than or equal to 500 μm, air (bubble) flows out easily so that the effect can no longer be obtained. Further, if the depth of the grooves 31 is smaller or equal to 10 μm, the effect cannot be obtained and if it is greater than or equal to 500 μm, strength of the core plate 20 is lowered.
The uneven portions 32 are formed regularly or irregularly on the bottom surface 21a of the oil passage 21. The uneven portions 32 are formed in such a manner that after the adhesive agent 22 is applied to the core plate 20, the bottom surface 21a of the oil passage 21 between the friction material segments 12 is made rough by shot blast to have 5 μm in Ra (arithmetic average roughness).
The surface roughness of the uneven portions 32 are preferably 0.1 to 10 μm in Ra (arithmetic average roughness). This is because the effect cannot be obtained if it is less than or equal to 0.1 μm and a discharge property of oil is deteriorated if it is greater than or equal to 10 μm.
The uneven portions 32 may be partially provided, but are preferably provided in all regions of the oil passage 21.
The projections 33 are formed in such a manner that the adhesive agent 22 is applied to the core plate 20 and subsequently a die on which minute holes having a diameter of 200 μm and a depth of 200 μm are formed is pressed under a constant pressure against the oil passage 21 between the friction material segments 12 so that the plurality of projections 33 are formed on a surface of the layered adhesive agent 22 or the core plate 20.
The plurality of projections 33 may be formed in a columnar shape, a conical shape, a pyramidal shape or the like. They may be formed in one of a columnar shape, a conical shape and a pyramidal shape or a combination thereof. They preferably have a radius of 0.1 to 1 mm, a height of 0.01 to 0.3 mm, and an area rate of 10 to 50% to the bottom surface 21a of the oil passage 21. Furthermore, they are irregular in size and are not uniform in size.
It is not preferable that each of the projections 33 has a radius smaller than or equal to 0.1 mm, since the effect cannot be obtained, and it is not preferable that each of those has a radius greater than or equal to 1 mm, since an adverse effect influences on a discharge property of oil. Further, it is not preferable that each of those has a height less than or equal to 0.01 mm, since the effect cannot be obtained, and it is not preferable that each of those has a height greater than or equal to 0.3 mm, since an engagement property is deteriorated due to a possibility of contact with a counterpart plate. Furthermore, the height may be uneven. It is not preferable that an area rate of a total area of the plurality of projections 33 to an area of the bottom surface 21a of the oil passage 21 is less than or equal to 10%, since the effect cannot be obtained, and it is not preferable that an area rate of a total area of the plurality of projections 33 to an area of the bottom surface 21a of the oil passage 21 is greater than or equal to 50%, since an adverse effect influences on a discharge property of oil.
In each of the above-mentioned embodiments, in order to obtain the effect by the forming portion satisfactorily, it is preferable that the friction material segments 12 are provided with the oil grooves 12b opened at only the outer diameter side. This is because the oil dragged in the friction surface 25 from the oil passage 21 is discharged to the outer diameter side smoothly and the drag torque can be lowered during idling. The effect of reduction of drag torque is remarkable specifically in the low rotation region.
Depending on shapes of the friction material segments 12, it is not necessary to provide forming portions for retaining air all between the friction material segments 12. Further, in a case where a friction material segment has a shape by which an oil discharge property is deteriorated and a drag torque becomes great in the low rotation region where the effect is aimed at, it is preferable to partially decrease a number of places where the forming portion is formed.
In a case where the fiction material segments 12 are constituted by not a segment-shaped friction materials but a ring-type (annular) shaped one, a minute hole, an uneven portion or the like is formed on a molding die correspondingly to a portion becoming the oil passage 21, and a minute groove, an uneven portion or a projection can be formed by performing transfer on the bottom surface 21a of the oil passage 21, so that the same effect as described above can be obtained.
In each of the embodiments, the minute grooves, the uneven portions or projections are formed on the surface of the core plate 20 or on the adhesive agent 22 applied to the surface of the core plate 20 as the forming portion. However, a forming portion can be formed in such a manner that a sheet-like member provided with minute grooves, uneven portions or projections may be adhered to the surface of the core plate 20 or the adhesive agent 22.
(Evaluation Test Results)
Shown hereinafter will be evaluation test results of friction plates according to each embodiment of the present invention and a comparative example (prior art). Table 1 shows evaluation conditions and a graph of
Evaluation tests have been conducted with a drag torque measurement testing machine under the test conditions described in Table 1.
TABLE 1
ITEM
CONDITION
NUMBER OF ROTATIONS
0-5000
(rpm)
DIAMETER OF WET
φ157
FRICTION TYPE PLATE
(mm)
NUMBER OF FRICTION
3
PLATES(NUMBER OF
PLATES)
LUBRICANT (AXIAL
0.5
CENTER: L/min)
OIL TEMPERATURE (° C.)
40
In the graph of
As will be appreciated from
The present invention having been described above is not limited to each embodiment mentioned above and the friction material segments can be formed into shapes other than the illustrated shapes. Further, the invention can be applied to a friction material segment having an oil groove different in configuration or having no oil groove. Note that it is needless to say that the grooves, the uneven portions, and the projections are illustrated not in actual dimension but in exaggerated form for convenience of explanation. Further, the forming portions such as the grooves, the concave convex portions and the projecting portions can be formed integrally with the bottom surface (namely, the surface of the core plate 20) of the oil passage.
The invention having been explained above can be used for vehicle and the like in which an automatic transmission is installed.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2015-042084, filed Mar. 4, 2015, which is hereby incorporated by reference herein in its entirety.
Kobayashi, Masato, Natsumeda, Shinichi, Miyazaki, Tomoyuki
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